Our work involves the development of methods of computer-analyzed two-dimensional gel electrophoresis of proteins for the quantitative studies of the proteins of differentiated cells. We have refined the methods of two-dimensional gel electrophoresis, and we have built a semi-automated laboratory specialized for two-dimensional electrophoresis which helps us to produce many two-dimensional gels each year with high resolution and reproducibility. Much of the equipment in this new laboratory is controlled and monitored by a microcomputer system and computerized data management programs have been written to keep accurate records of all experimental samples, gels and films, as well as quality-control data on all reagents used for gel electrophoresis. Image processing programs have been written for quantitative analysis and matching of the complex protein patterns that appear on autoradiograms or fluorograms of two-dimensional gels. This facility is being used to study the proteins of differentiated rat and mouse cells. We are establishing a permanent data base which will contain information on the types and amounts of several thousand proteins synthesized by a number of different cell types. Each protein in the data base will be identified by a set of standard coordinates. Such a data base will allow comparisons and correlations of protein patterns between many cell types in various states of growth and differentiation.